Uffe Elbæk of The Alternative visits Skagen in northern Denmark as part of his election campaign.
Photograph: Scanpix Denmark

They have campaigned for a 30-hour working week, for 100% organic agriculture in Denmark, and meat-free days in public institutions. Now, The Alternative – a political party formed less than two years ago to champion a green agenda – could hold the key to power in Denmark’s general election next week.

Danish elections 2015: a guide to the parties, candidates and electoral system

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As Denmark goes to the polls on Thursday, the Social Democrat-led alliance led by the country’s first female prime minister, Helle Thorning-Schmidt, is locked in a tight election battle with a centre-right blue bloc and the leader of the Liberal party. Seats won by The Alternative could nevertheless help secure another term in power for her.

“It’s the perfect position for us to be in,” said Uffe Elbæk, leader of The Alternative and a former minister of culture under Thorning-Schmidt’s government. “Everyone now has to deal with us – whether they like us or not.”

The prime minister certainly looked to have paid attention. Asked during a TV debate whether she thought Elbæk was on to something with his political ideas, Thorning-Schmidt said: “Yes, I think so. I also have an inner hippie who likes to wear colourful clothes, relax and have meat-free days.”

Thorning-Schmidt speaks at a political festival. Photograph: Jacob Crawfurd/Demotix/Corbis

Critics have labelled The Alternative a joke and attacked its policies for being unsubstantiated and fanciful – one of its members floated the idea of solar-powered cycling pipelines that would generate tailwind – but the party has struck a rich vein among disillusioned voters who find the old parties closely aligned on core issues and lacking ambition.

Speaking at their party headquarters in Copenhagen, where lime-green election posters were on display in the windows and a stack of T-shirts carried words such as “generosity”, “humour” and “transparency”, Elbæk said The Alternative was part of a wider international movement demanding a new political culture.

I also have an inner hippie who likes to wear colourful clothes, relax and have meat-free days

Helle Thorning-Schmidt, Danish prime minister

He pointed to Podemos in Spain as a potential collaborator in Europe. “If we succeed in this election, then this is another step in the direction of moving from a representative democracy to an involving democracy,” he said. “We have to legitimise democracy.”

While public sector spending, welfare and immigration have dominated the election debate in Denmark, the future of Europe came to the fore last week. The opposition parties, led by the normally pro-European Liberal party, announced they would back David Cameron in his quest for renegotiation to prevent the EU turning into a “social union”.

Danish opposition leader Uffe Elbaek of The Alternative is photographed at the party’s headquarters in Copenhagen. Photograph: Linda Kastrup/Reuters

The eurosceptic Danish People’s party looks set to cement its position as Denmark’s third-biggest party after the election, and the agreement was seen as another sign of its renewed pressure on the opposition for wider EU reforms.

Everyone now has to deal with us – whether they like us or not

Uffe Elbæk

“A very powerful Danish People’s party will have implications,” said Kasper Fogh Hansen, a political commentator and former Social Democratic campaign adviser. “Denmark is on a political trajectory where people are very skeptical about a European community that can’t handle the migration of workers and the pressure of immigrants and refugees. The political direction will be the same whether it’s a red or blue government, but there might be more draconian measures from the right.”

As Denmark earlier this month celebrated the centenary of its constitution and women’s right to vote, Thorning-Schmidt spoke outside the parliament building, Christiansborg, amid a sea of red banners and the reverberating bass from a nearby soundsystem. She was preceded on stage by a male dance performer wearing only a pair of sand-coloured skimpy shorts, as early summer sun and street parties engulfed Copenhagen. The prime minister put party politics aside in her speech, but the battle for Borgen was preoccupying the crowds.

The Danish royal family and prime minister at Christiansborg in Copenhagen. Photograph: Splash News/Corbis

“I want her to continue in office but it has not worked as well as I thought under the current centre-left government,” said Karen Wolf, a 57-year-old business consultant from Copenhagen.

“I’m disappointed that they haven’t carried through with some of their ideas – but the opposition is a frightening prospect.”

Broken promises – from a proposed congestion charge in Copenhagen to a cap on student numbers in school classes – have been recurring points of attack for the opposition, which has led opinion polls since the last election. Social Democratic voters have been dismayed by what they see as a shift to the right for the party, including a toughened stance on immigration. Selling a stake in Denmark’s biggest utility to Goldman Sachs put the government on the brink of collapse, while speculation has been rife over Thorning-Schmidt’s future as she was touted for a top EU job.

But the last three weeks have seen a remarkable comeback by the prime minister and her red bloc, who have turned around a large poll deficit to leave them neck and neck with the opposition before Thursday’s vote. Part of the reason for this, and the biggest obstacle on the road back to power for the centre-right blue bloc, is a series of expenses scandals that have dogged the Liberal party leader, Lars Løkke Rasmussen.

“We can chose between two leaders with a character problem,” the newspaper Politiken wrote after the election was called. “Lars Løkke Rasmussen apparently doesn’t have any personal character, while Helle Thorning-Schmidt doesn’t have any political character.”

Helle Thorning-Schmidt poses for a selfie with a voter in Ringsted. Photograph: Ole Jensen/Demotix/Corbis

Turning the focus from politics to personalities appears to have played into the hands of the incumbent prime minister.

“Thorning-Schmidt was never popular,” says Fogh Hansen. “She was just a lot less unpopular than her opponent. If the blue bloc loses this election, it is down to the very poor choice of keeping a thoroughly scandalised Rasmussen as their candidate for prime minister. But their politics are victorious.”

According to Martin Krasnik, a TV anchor for national broadcaster Danmark’s Radio, personality has never before played such a crucial role in Danish elections, something which he says has generated fertile ground for new political parties, including The Alternative.

Krasnik said: “The crucial divide in Danish politics no longer runs across the centre. The two main parties – the Social Democrats and the Liberals – do everything they can not to position themselves on either side on major issues such as integration, asylum, economy and security. Now, the divisions can be found further out on the edges, and that’s why the most interesting discussions are taking place among the other parties.”